Exemplary embodiments relate to semiconductor devices and a method of manufacturing the same and, more particularly, to nonvolatile memory devices and a method of manufacturing the same.
A NAND flash memory device is an example of a nonvolatile memory device that includes a memory array of a plurality of memory blocks. Each of the memory blocks may include a plurality of memory strings. The memory string is coupled between a bit line and a source line. More specifically, the memory string includes a drain select transistor having a drain coupled to the bit line, a source select transistor having a source coupled to the source line, and a plurality of memory cells coupled in series between the select transistors (that is, the drain select transistor and the source select transistor).
In general, the memory string is formed on a substrate as a 2-D structure. In order to increase the integration degree, the cell size is to be reduced. However, further reductions in the cell size are reaching physical limits. For this reason, there is proposed a memory string having a 3-D structure in which the memory string is vertically formed on the substrate.
In order to vertically form the memory string on the substrate, conductive layers for word lines or select lines (that is, a drain select line and a source select line) are formed on the substrate at desired intervals. Insulating layers are formed between the conductive layers. A layer for forming the channel of the memory string (hereinafter referred to as a vertical channel layer) is formed in a vertical direction to the substrate through the conductive layers and the insulating layers. A multi-layer, including a charge trap layer and an insulating layer, is formed on a surface of the vertical channel layer. Consequently, the multi-layer is formed between the vertical channel layer and the conductive layers.
As described above, the memory string having a 3-D structure is significantly different from the memory string of the 2-D structure in the manufacturing method. The memory string of the 3-D structure may not have high structural reliability due to such a different manufacturing method.